End mill grinder

ABSTRACT

A production type machine is designed to grind end mills at a high rate while maintaining rigid standards of accuracy of dimension. Adjustments are quickly and easily made for different profiles of the ground face, the number of flutes on the mill, the size of the end mill, and so on. The machine will selectively grind either a curved cutter face, or an angular primarysecondary relief form thereon. Operation of the apparatus is fully automatic once the grind cycle is started, after necessary adjustments are made, as only the loading and unloading operations are manually performed.

United States Patent 1191 Borchert, III June 18, 1974 END MILL GRINDER 1Primary Examiner-Al Lawrence Smith [75] Inventor. Ernst Borchert, III,Pomona, Calif. Assistant Examiner NicholaS P. Godici s gne -WinslowAerospace Tool Attorney, Agent, or Firm-Wolfe, Hubbard, Leydig,

Co., Portland, Oreg. Voit & Osann, Ltd. [22] Filed: June 29, 1972 21Appl. No.: 267,437 [57] TM A production type machine is designed togrind end mills at a high rate while maintaining rigid standards [52]US. Cl 51/96, 51/225, 51/234 of accuracy of dimension Adjustments arequickly [51] Int. Cl B241) 3/06, B24b 7/02, B24b 9/00 and easily made fdifferent profiles of the ground [58] new of Search 51,96 124 219 face,the number of flutes on the mill, the size of the 5 1/234 16578 endmill, and so on. The machine will selectively grind either a curvedcutter face, or an angularprimary- [56] References C'ted secondaryrelief form thereon. Operation of the appa- UNITED STATES PATENTS ratusis fully automatic once the grind cycle is started, 2,853,994 9/1958Ronches 125/11 AT after necessary adjustments are made, as y the3,318,050 5/1967 Leckington... 5l/96 loading and unloading operationsare manually per- 3,623,277 ll/l97l Bottcher et a 5l/l24 R X formed,3,680,262 8/!972 Aydelott et al. 51/96 3.719.459 3/1973 Southland 51/967 Clams, 40 Drawmg Flgures PATENTEflJunam 3.818995 sum 01 or 12PATENTEDmw an sum ion or 12 SHEEI 05 0F 12 PATENTEDJun w an mmmmmm3816395 sum can; 12

PATENTEDJumm 13.816995 sum near 12 sum 10 or 12 PATENTEDJuu 18 I914 1END MILL GRINDER BACKGROUND OF THE INVENTION 1. Field of the InventionThe present invention relates generally to automatic grinding machinesfor end mills, and particularly to improvements in a grinding machine,such as disclosed in US. application Ser. No. 140,972, of John RobertSouthland, converting this machine to offer two optional capabilities,first, an arcuate relief grind, and second, an angular primary andsecondary relief grind. The arcuate relief grind, made by the machine ofUS. application Ser. No. 140,972, now U.S. Pat. No. 3,719,459, hascertain advantages, but the angular, primary/secondary grind retains atthe present time a preponderance of adherents. The general purpose ofthe invention is therefore to furnish the original grinding machinereferred to hereinabove with a novel alter- 2 natively selective cycleof movements, differing from that of application Ser. No. 140,972, nowUS. Pat. No. 3,719,459, and with certain additional features, whereby agrind of the angular, primary/secondary relief type may be produced.

2. Summary The grinding machine of the invention includes a suitableframe, with a powered grinding wheel thereon. A holder is provided forthe end mill, and the holder is mounted on a movable workhead. Theworkhead is mounted on the machine frame for movements in either of twoselective basic sequences, differing both in kind and in sequence, togrind the end mill to either a continually curved form, or an angularform consisting of two angularly related primary and secondary faces.For the first grind, the end mill is advanced toward the grinding wheel,then swung relative to and along the grinding wheel on a predeterminedaxis, to obtain the desired arcuate shape on the end mill cutter, thenretracted and swung back to its initial position and thereafter indexedto bring the next end mill cutter face into position, whereupon thecycle is repeated. The present invention is selectively operable tocarry out a modified cycle, according to which the end mill is fedstraight into and against the grinding wheel, while disposed at aselected secondary relief angle to the direction line of feed. A plungegrind at the secondary relief angle is thus made. The end mill is thenretracted, then swung to the selected primary relief angle, and then fedback in, at this primary angle, to effect a second plunge grind, thistime at the selected primary angle. The end mill is then retracted andthereafter rotated on its axis to index for the next cutter face. Theinvention includes adjustable stops and coacting arrangements forpositioning the end mill at the selected primary and secondary anglesfor the specific grind desired.

BRIEF DESCRIPTION OF THE DRAWINGS Reference is now made to the followingdescription and to the annexed drawings, in which:

FIG. 1 is a front and side perspective view of an end mill grinderembodying the present invention;

FIG. 2 is a fragmentary perspective of the end of an end mill blank;

FIG. 3 is a fragmentary perspective showing the relative position of theblank and the grinding wheel during start of the first face grind on theblank;

FIGS. 4 and 5 are diagrammatic views showing different shapes ofsurfaces ground on an endmill, only one longitudinal half of the endmill being shown;

FIGS. 6A to 6F are successive diagrammatic views showing the relativemovement of the end mill during a cycle of operations for grinding atone flute to produce a known arcuate grind such as shown in FIG. 4;

FIGS. 6G to 6N are successive diagrammatic views showing a differentoperation, to produce the primary, secondary grind of FIG. 5;

FIGS. 7A, 7B and 7C are three side elevations of the discs comprisingthe flute selector means illustrating different relative positions ofthe two discs, according to the number of flutes on the end mill beingground;

FIG. 8 is a fragmentary vertical longitudinal section approximately online 8-8 of FIG. 1 showing in side elevation the workhead for holding anend mill, the section passing through both the swing axis for theworkhead and the grinding wheel axis;

FIG. 9 is a front and top perspective, with enclosure removed, of theworkhead and mounting means therefor viewed from the left in FIG. 8, thelower portion being in section;

FIG. 10 is a vertical median section through the workhead on line 10l0of FIG. 9;

FIG. 10a is an enlarged fragment of FIG. 10 with the tool holderremoved;

FIG. 11 is a fragmentary combined elevation and section showing themounting means for the end mill locator;

FIG. 12 is a vertical transverse section taken substantially on line12-12 of FIG. 10;

FIG. 13 is a fragmentary horizontal section on line l313 of FIG. 12showing the drive from the hydraulic motor to the ring gear of theworkhead;

FIG. 14 is a fragmentary vertical section substantially on line l4l4 ofFIG. 13 showing the output shaft from the hydraulic motor for theworkhead;

FIG. 15 is a fragmentary horizontal section through the mounting meansfor the workhead taken substan tially on line 15-15 of FIG. 9 or FIG.12;

FIG. 16 is a fragmentary vertical section through the flute indexingmechanism taken substantially on line l6-16 of FIG. 9, FIG. 10 or FIG.17;

FIG. 17 is a fragmentary vertical section taken on line l717 of FIG. 9or FIG. 16;

FIG. 18 is a fragmentary perspective of the means for moving theworkhead;

FIG. 19 is a longitudinal median section through the tool holder;

FIG. 20 is a schematic of the electric circuit;

FIGS. 21A and 21B taken together comprise a schematic drawing showingthe air-hydraulic control system and the component parts operated andcontrolled thereby, the pneumatic logic units being shown symbol icallyaccording to the legend on the figures;

FIG. 22 is an operating diagram showing the movements of the variousparts during a sub-cycle grinding of a single face on the end mill;

FIG. 23 is a diagram similar to .FIG. 22 but showing the events when themachine produces an angular primary/secondary type grind.

DESCRIPTION OF A PREFERRED EMBODIMENT The end mill grinder has a frame Fon which is mounted a workhead H in which the tool to be ground isplaced. To effect the desired movement of this workhead and the tooltherein, support and actuating means S are provided on the frame. Toeffect automatic control of the duration and sequence of the variousmotions of the machine required to successively grind cutter faces onthe tool, one for each flute on the end mill, there is provided anair-hydraulic control system which includes pneumatic logic unitsinterconnected appropriately for the functions to be carried out. Such asystem is shown schematically in FIGS. 21A and 21B. In each of thesefigures are pneumatic lines ending at terminals such as 1, 2, 3, and thesystem is complete when the like terminals of FIGS. 21A and 21B, such as1,1, 2,2, 3,3, etc. are connected together. The pneumatic lines of thesefigures are also identified by the numerals of the terminals to whichthey are connected. In FIG. 21A, hydraulic lines, which carry thehydraulic fluid from the various hydraulic work cylinder and pistonassemblies are distinguished by heavy lines with arrows thereondesignating flow directions, while lines without arrows are pneumaticcontrol lines and these are in circuit with the pneumatic logic circuit(FIG. 21B).

GENERAL OPERATION Assume first that a curved face grind (FIG. 3) is tobe produced. In FIG. 2 is shown a fragment of a four fluted end millblank B which has an end face to be sharpened or ground, in this casewith a corresponding number of arcuate end cutting faces 30a. Grindingis accomplished by bringing face 30 on the ene mill into contact withthe periphery of a grinding wheel 31 normally thereto (FIG. 6B), andwith its longitudinal axis 58 substantially in the plane of the topsurface of the grinding wheel, so that the peripheral grinding surfacewill be tangent to only the lower half of the end of the blank B. Asindicated in FIGS. 6A and 6B, the end mill approaches the grinding wheelwith its axis 58 parallel to but laterally offset from a plane 47 thatis at right angles to the grinding wheel, and that passes through thegrinding wheel axis. The end mill is then swung in a horizontal plane onan axis 32 which is in the plane 47, and is parallel to the grindingwheel axis, so as to move to the position of FIG. 6C. Thereby isproduced arcuate end face 30a, sweeping away from the beginning radialline of the grind on a downward or inward arcuate curve, and producing aradial cutting edge or lip e for the next succeeding face 30a to beground. The end mill, after termination of such a grind by swingingmovement about axis 32, is shown in FIG. 3 (corresponding to FIG. 6C),with face 30a ground, and a radial lip e formed. The end mill isindexed, by rotation through 90, for example, for a four flute end mill,following each face grind, so there will be one cutting edge or lip eand face 30a for each flute on the end mill. The shape in profile of theground face 30a (to provide clearance) may be smoothly curved, as shownin FIG. 4. By certain changes, under selective control, the face may beground to have instead a substantially flat, angular, primary reliefarea 3012 adjacent the lip e, at a primary relief angle Q5, andtherebeyond a second steeper area 300 disposed at a secondary reliefangle 9 (FIG.

5). This latter grind is known as a primary/secondary relief grind.

FIGS. 6A-6F show the sequence of movements to accomplish the arcuategrinding face form of FIGS. 3 and 4.

First, the end mill blank B is hand loaded into the workhead andproperly positioned, as shown schematically in FIG. 6A. Next, the endmill feeds in endwise toward the grinding wheel to engage the wheel asshown in FIG. 68 after which one face grind forming a cutting lip e issupplied by swinging the end mill as shown in FIG. 6C about the swingaxis 32. The swing axis 32 is vertical and parallel to the axis 35 ofthe grinding wheel. It is also offset laterally from axis 58, in avertical plane 47 parallel with axis 58 and substantially throughgrinding wheel axis 35.

After the grinding pass, the end mill is retracted FIG. 6D), and it thenswings back about the swing axis to its position at FIG. 6E, followingwhich the end mill blank is indexed as at FIG. 6F by rotating is aroundits longitudinal axis 58 to bring it into position for grinding anotherarcuate face 30a and lip e on the end face 30. The grind sub-cycle shownin FIG. 22 for the various positions of FIGS. 6A to 6F is then repeatedaccording to the number of flutes on the mill with an indexing rotationtaking place between each two grinding subcycles, except that after thelast grind, the grind cycle is terminated.

GRINDING WHEEL ASSEMBLY The grinding wheel 31 is rotatably mounted onthe frame by spindle 33 joumalled in bearing housing 34. SPINDLE 33mounts the grinding wheel to turn about vertical axis 35 and is drivenfrom motor 36 by one or more belts 37 which pass from the output shaftof the motor to a drive pulley mounted on an extension of spindle 33.Spindle housing 34 and motor 36 are mounted on adjustable block 38 onframe F.

WORKHEAD workhead H has upper and lower trunnions shown at 45 in FIG. 10and 46 in FIG. 8, respectively. These trunnions are mounted in the upperand lower arms 45a and 45b of carriage which is in the form of a yoke,and they establish the vertical swing axis 32 about which the workheadand the end mill swing. Axis 32 is parallel to grind wheel axis 35 andthe two axes preferably lie in or close to a common plane indicated at47 in FIGS. 4 and 5.

To adapt the workhead to hold end mills of different dimensions, the endmill blank is placed in a removable tool holder 48 illustrated in detailin FIG. 19. The external housing of the tool holder remains constant insize in order that the holder may be held firmly in the workhead, butthe holder has an internal sleeve 49 which engages collet 50 that isreplaceable in order to provide a collet of the proper size, to hold endmills of different diameters and lengths. The inner sleeve 49 isspringbiased by a spring 49a to urge collet 50 to the left in FIG. 19and into a closed or gripping position, but the end mill can be releasedby grasping handles 51 and manually bringing them together to relievethe pressure of spring 49a and sleeve 49 on collet 50.

Tool holder 48 is held within the workhead by a chuck comprising a pairof spaced bearing sleeves 53 and 54 which receive the tool holder with asnug-sliding fit. Between sleeves S3 and 54 is collet 55 which can beclosed by movement of an hydraulically actuated piston 56 (to the rightin FIG. to firmly grip the exterior of tool holder 48.

As may be seen better in FIG. 10A, hydraulic fluid under pressure isadmitted to the lefthand face of piston 56 through fluid passage 56.1 inthe head and an annular distribution passage 56.2 in the periphery ofsleeve 54. The force exerted by the fluid moves piston 56 to the rightagainst spring 56.3 which normally urges the piston to the position ofFIG. 10 in which the collet is open. Movement of the collet to the rightcloses the collet, by engagement with inclined surface 56.4, to griptool holder 48.

When collet 55 is released, the tool holder isfree to move axially orrotationally about longitudinal axis 58, which is also the longitudinalaxis of blank B when mounted in holder 48. Workhead H establishes axis58 at a known position with respect to grind wheel 31.

The location of longitudinal axis 58 is indicated in FIGS. 4 and 5 fromwhich it will be noticed that this axis is laterally offset from and isparallel to plane 47 which passes through swing axis 32 and wheel axis35. The spacing or offset between plane 47 and axis 58 is variable bymeans to be described. The magnitude of this offset affects the shape ofthe ground surface 30a of the end mill and consequently is closelycontrolled. Typically, the magnitude of the offset varies between 0 and0.200 inches.

The Workhead is divided into front and rear halves H, and Hrespectively, more or less along a vertical transverse plane 60illustrated in FIG. 10. The two halves are relatively rotatable to oneanother on an axis 62, bur firmly clamped together by an annularclamping band 61 which is provided with screw 61a by which it can betightened to firmly hold the two halves of the head in adjustedpositions. It will be seen by reference to FIG. 12 that the geometriccenter 62 of the two halves of Workhead H is above axis 58, that is, itis eccentric with respect to axis 58. Consequently, when the front halfH,, or face plate, in which the tool holder 48 is held, is rotated aboutthe geometric center 62 with respect to the rear half H of the Workhead,the tool holder 48 moves in a short horizontal arc and thereby thelongitudinal axis 58 of the tool can be moved toward or away from plane47 in order to establish the desired magnitude of the offset betweenplane 47 and axis 58.

The amount of this offset is indicated by a graduated scale 63 on thefront of the Workhead (FIG. 9) and a pivoted index arm 64 actuated bylink 65 connected to the arm and to the front half of the Workhead.Adjustment is accomplished with clamping band 61 released by backing offscrew 61a.

The rear half H of the workhead carries the trunnions 45 and 46 andconsequently is fixed relative to v the aforementioned Workhead carriageor yoke 120,

except for rotation about vertical axis 32.

Recessed and rotatable in the forward face of the rear half H of theWorkhead is ring gear 66 (FIGS. 10 and 12). The periphery of the ringgear is smooth and provides a bearing surface for the gear as it turns.It is provided with internal teeth which, as shown in FIG. 12, mesh withthree spur gears 67, 68 and 78. The lower one of these spur gears 67comprises teeth out on the periphery of bearing sleeve 54 wherebyrotation of the ring gear turns bearing sleeve 54 and tool holder 48when collet 55 is tightened since the collet frictionally 6. locks thetool holder to the front bearing sleeve 53 and the two sleeves 53 and 54are connected by pins (not shown) to transmit torque from one sleeve tothe other.

Ring gear 66 is rotated by a second spur gear 68 on a short horizontallyextending shaft. 70 mounted in suitable bearings in the rear half ofhead H. Shaft 70, shown in FIG. 13, also carries a second gear 71 whichmeshes with worm gear 73 driven by shaft 74 from the output shaft ofhydraulic motor 75. Hydraulic motor 75 may be of any suitable design, agear or lobe type positive displacement motor having a rotary outputmember being preferred.

FIG. 12 shows the Workhead substantially as it would appear if the fronthalf of the head were removed. From this view, it is apparent that asring gear 66 rotates, for example in a clockwise direction, gear 67likewise rotates clockwise about axis 58. This rotates tool holder 48with the blank B to index the blank by the angle between successiveflutes. The sequence and control of this movement will be discussedlater.

As illustrated in both FIGS. 10 and 12, there also meshes with ring gear66 a third spur gear 78which is driven by movement of the ring gear.This gear is an input to the flute selector mechanism which is adjustedmanually by the machine operator in order to index automatically thetool as required according to the number of flutes on the blank beingground. The flute selector mechanism is generally indicated at 80 and isshown in detail in FIGS. 16 and 17.

Spur gear 78 is attached to shaft 81 (FIG. 10) which is rotatablymounted in the rear half of Workhead H and which carries at its rear endbevel gear 82. Bevel gear 82 meshes with a second bevel gear 83 mountedon shaft 84. Shaft 84 is mounted in suitable bearings, as shown in FIG.16, in a housing constituting part of the Workhead structure. Shaft 84extends forwardly beyond the housing and carries at the outer exposedend knob 85 which is preferably provided with an index mark 86 as shownin FIG. 9.

Mounted on shaft 84 to rotate therewith is a first selector disc 87.Adjacent disc 87 is a second selector disc 88 mounted coaxially of disc87 on a hub89 which surrounds the extension of shaft 84 and carries onits outer free knob 90. Knob 90 carries indicia which cooperate withindex 86 to indicate to the machine operator the relative positions ofthe two discs 87 and 88.

One of the discs, typically disc 87, carries a fixed pin 91 which can belocated in aselected one of a plurality of openings 93 in disc 88. Inorder to locate pin 91 in a selected opening 93, disc 88 is mounted foraxial slid ing movement on shaft 84; but it is biased by spring 94 tothe position shown in engagement with disc 87, thereby keeping pin 91 ina selected opening 93. To change the location of the hole in which pin91 is placed, the operator can grasp knob 90, pull it outwardly on shaft84 thereby compressing spring 94 and freeing disc 88, and turning theknob to bring another hole into registration with pin 91. Release ofknob 90 then allows the pin to enter the newly selected hole under thebiasing action of spring 94.

The relationship to eachother of the two discs 87 and 88 of the fluteselector mechanism is shown schematically in FIGS. 7A to 7C whichillustrate three different positions of the discs.

Since end mills are nonnally provided with two, three, or four flutes,provision has been made in the preferred embodiment for only thesenumbers of flutes, but it will be understood that in the broad sense theinvention is not so specifically limited. Referring now to FIGS. 7A to7C, it will be noticed that disc 87 has around its periphery a pluralityof notches 87a. Likewise, disc 88 has around its periphery a series ofnotches 88a. These notches in the peripheries of the two discs are solocated that various combinations of the notches are brought intoregistration with each other by relative rotation of the discs withrespect to each other. Two notches in registration form a gate.

For example, in FIG. 7A, two pairs of notches 87a and 88a, spaced 180apart around the discs, are brought into registration when pin 91 is inthe center one of the three holes 93 in disc 88. This is the conditionexisting when it is desired to index the tool for two flutes, it beingnecessary to rotate the tool 180 between contacts with the grindingwheel.

When the tool has three flutes, disc 88 is shifted to the position ofFIG. 7B in which three pairs of notches 87a and 88a spaced 120 apartaround the periphery of the discs are in registration, as shown.

In the case of a four-flute mill, the two discs can be rotated to theposition in FIG. 7C in which four pairs of notches are in registration,as shown. The relative positions of the two discs are displayed to theoperator by the cooperation of index 86 and markings on knob 90 whichare shown schematically in FIGS. 7A, 7B, and 7C.

The object of this arrangement of the two selector discs is to presentto a subsequently described indexing control pin 96 a number of gates inthe form of peripheral indentations, equal to the number of end millflutes and equally spaced around the periphery of the combined discs.Entry of the control pin into the peripheral gate results in delivery ofa signal for the later mentioned control system (FIGS. 16, 17, 20 21Aand 2113). The control system can be any capable of carrying out thenecessary programmed sequence of machine operation, and a suitablealternative could be supplied readily by those skilled in the art. Forsimplification, therefore, the present control system is describedgenerally but details of some unclaimed components, particularly thelogic circuit, are left to illustration in drawings which can readily beunderstood by those skilled in the art.

In general, with the disks 87 and 88 rotating during an indexing period,a pneumatic signal produced by the entry of control pin 96 into aperipheral gate provided by a pair of notches 87a and 88a in mutualregistration conveys the information to the control system that therotating tool B is now approaching a new position at which the machineis to perform again the grind subcycle of operation illustrated in FIGS.6A to 6F. How ever, in order to terminate the grinding operation afterone complete revolution of discs 87 and 88, representing a completerevolution of tool B, one gate, for example, the one at the upper rightportion of FIG. 7A, is made radially deeper than all others. Upon entryinto the deeper gate, the greater radial inward movement of the controlpin 96 conveys to the control system the additional information that allfaces of the particular end mill blank in the machine have now beenground.

Control pin 96 is mounted on swinging link 98 which is pivotallyconnected to one end of spool 99 in hydraulic valve 100. Also connectedto link 98 is bell crank 101 which is pivoted at 102 to a fixed portionof the frame. One arm is pivoted at 103 to spool 104 of pneumaticcontrol valve 105 while the other arm of bell crank 101 is coupled tolink 98 by pin 196 sliding in a slot in link 98 allowing relativemovement between the pin and the link 98. Movement of pin 96 radially ofselector discs 87 and 88 causes bell crank 101 to swing about its fixedpivot 102 and thereby shifts spool 104 longitudinally of valve 105.

When indexing an end mill blank, shaft 84 and the selector discs 87 and88 turn in a counterclockwise direction viewed in FIG. 17. During thismovement, control pin 96 rides against the circumference of one or bothdiscs 87 and 88, under a force applied as later described.

When one of the gates passes under index control pin 96, the control pinenters the gate and moves a short distance with the discs, link 98moving toward the upper left in FIG. 17, thus shifting spool 99 of thevalve 100 upward. This valve is a two-position valve and is in serieswith the supply of hydraulic fluid to motor 75. In the lower position,the valve is open and allows full flow of hydraulic fluid to the motorto accomplish indexing rotation of the end mill. In the upper position(full lines in FIG. 210), the valve 100 reduces the flow and deceleratesmotor 75 but does not shut off hydraulic fluid flow entirely. The motor75, however, is stopped by a presently described locking pin 107. Motionof pin 96 is also transferred by link 98 to pin 106 which in turn actsthrough bell crank 101 to shift spool 104 of valve 105 between threelater described positions to control flows of air in a suitable controlsystem, such as shown schematically in FIG. 21A and 21B.

The final position of the end mill B after each indexing rotation isdetermined by lock pin 107 FIG. 21A) which is reciprocated toward andaway from chuck sleeve 53 by pressure of air or hydraulic fluid on oneof pistons 108 and 108a, moving within cylinder 109 on the workhead.Check sleeve 53 has around its periphery a plurality of notches 53a anyone of which may be entered by locking pin 107 when aligned with the pinand the pin is pressed down. When pin 107 is in the raised or retractedposition, it is out of the notches 53a and check sleeve 53 is free toturn under torque imparted to it from ring gear 66 driven by motor 75.

Locking pin notches 53a correspond in number and location to the gatesprovided by discs 87 and 88. When control pin 96 is out of a gate andspool 104 is in its lowermost position (FIG. 17), valve 105 signals thecontrol system to withdraw the plunger 107, which permits indexing ofthe end mill blank. In the proper position in the angular movement ofthe chuck, pin 107 is moved toward chuck sleeve 53 by air pressureapplied to piston 108 and enters the appropriate notch 53a in thesleeve, as will be further described.

When pin 107 enters into a notch 53a, the hydraulic motor stops turning.Fluid supply to hydraulic motor 75 is reduced but not entirely shut offso that the motor urges the chuck against plunger 107 thus eliminatingany backlash or play in the system and bringing the end mill blankaccurately to the desired grind position.

The full indexing operation, following swing back of the head FIG. 615),is as follows;

Hydraulic pressure is applied at the end of swing back to the end ofpiston 1040 of valve spool 104 through valve W under control of thelogic circuit pneumatic line identified by terminals 4 (FIGS. 21A and21B). This pressure application, which initiates indexing, results fromcoaction of functions in the logic circuit of FIG. 21B owing toactuation of later described pneuamtic swing and feed end limitpneumatic switches V2 and V4 for the workhead (FlG. 21A) as the workheadreturns to the position of FIG. 6E. Spool 104 then shifts to the right,to the full line position in FIG. 17, lifting pin 96 out of a gap indiscs 87, 88 by means of bell crank 101 pivoted at 102. At this timealso constant system air pressure (from constant pressure sourceterminal 8) on piston 100a acts to shift spool 99 of valve 100 togetherwith link or lever 98 and pin 96 to the right pin 96 moving a distanceequivalent to about 15 of arc of the discs 87 and 88. The air linesthrough terminals 5 and 6 from the logic circuit are then open toatmosphere through valve 105 (FIG. 7), with the effect of conditioningor signalling the logic circuit to act through its line 7 to operatevalve Hy to send hydraulic pressure fluid to the underside of piston1080, thereby elevating locking pin 107 out of a notch 53a in chucksleeve 53. At this time, with the valve spool 99 in the position of FIG.17, held there by application of pressure fluid received from line 8,hydraulic fluid flows through valve 100 to hydraulic motor 75, rotatingit, the chuck sleeve 53 and the end mill through an indexing interval.

The hydraulic pressure to piston 104a is, after a short delay, then shutoff through operation of a timer in the logic circuit and the controlcircuit line 4 leading to valve W. The constant air pressure from line8, under piston 104a then acts through valve spool 104 and bell crank101 to cause pin 96 to bear against the periphery of discs 87 and 88,awaiting the next gap; and when the next gap reaches the pin 96, whichin this case is one of the shallow gaps, the pin is forced therein. Theair pressure on the underside of the piston head 104a then coacts withthe pin 96 engaged in the gap in the rotating disks to shift valve spool104 to the left, to the intermediate position indicated in phantom linesin F 1G. 17, and to carry the pin 96 counterclockwise through about ofarc.

At this time, the intermediate piston 1040 of spool 104 closes the portexhausting air from line 5 to atmosphere, and opens line 5 to pressureline 8, sending pressure to the logic circuit via line 5. This in turnacts through the logic circuit, line 7 and valve Hy to remove thehydraulic pressure from the underside of piston 108a. This allows theconstant air pressure applied to the top side of piston 108 to push thelocking pin 107 against the chuck sleeve 53.

The described motion of the pin 96 entered into a gap in the rotatingdisks has also carried the link 98 and the valve spool 99 toward theleft, and the lower piston of spool 99 then nearly, but not quite,closes the flow passage for supplying the hydraulic motor, which thenslows down to a low speed.

As the chuck sleeve notch 53a aligns with locking pin 107, said pin 107enters therein, locking the motor from rotation, and completes the indexsub-cycle.

As the locking pin 107 enters chuck sleeve notch 53a, piston 108 shiftsdownward in valve 109, applying pressure from line 8 to line 16, whichis sent to the logic circuit and signals it to start the next series ofoperations to grind the next face on the end mill.

After all end mill faces have been ground, the next following indexingrotation of the discs 87, 88, results in the pin 96 dropping into thedeep gap therein, causing the spool 104 to move to an extreme upperposition (not shown) with its piston 104a against stop 104a (FIG. 17).This connects open line 6 to pressure line 8 (as may be understood fromFIG. 21A). The rise in pressure in line 6 acts in the logic circuit tocancel all further turning and feed motions, and controls the workheadvia line 12 and valve U, and the hydraulic piston 53 and the elevatingcylinder 133, respectively, to release the collet and rise to the: loadposition, completing the cycle.

SUPPORT AND ACT UATION OF WORKHEAD The means or mechanism S forsupporting and moving the yoke 120 and workhead carried thereby, andultimately tne end mill held by the workhead, over a predetermined pathis disclosed in detail particularly in FIGS. 8, 9 and 18. It involves orproduces a compound movement of the workhead which has three majorcomponents: a vertical bodily lift and fall of the workhead and means Sas a whole; movement (F IG. 6B) of the yoke 120 and workhead about avertical axis 127 for causing feed and retraction of the mill blankrelative to the grinding wheel; and swing and swing-back (FIGS. 6C and6B) of the workhead only with respect to the yoke 120 about verticaltrunnion axis 32.

The yoke arms 46a and 46b of the aforementioned yoke 120 are verticallyspaced, and contain at their ends, the bearings for the trunnions 45 and46, respectively, which establish the swing axis 32. As seen best inFlG. 12, lower arm 46a of yoke is mounted, about midway of its length,on the upper end of a vertical inner sleeve 121, which is mounted forvertical reciprocation and angular oscillation in an external hearingsleeve 122. Bearing sleeve 122 contains a series of straight rows ofball bearings between the inner and outer sleeves. Bearing sleeve 122 ismounted within collar 124 which may be attached to the machine frame Fby bracket 125.

Within the concentric of inner sleeve 121 is vertically extending shaft126 whose longitudinal axis 127, which becomes the pivot axis for theyoke 120, is parallel to but laterally offset from the trunnion axis 32of the workhead. Shaft 126 extends above and below inner sleeve 121; andthe inner sleeve in turn extends below the bearing sleeve.

The lower end of inner sleeve 12:1 rests upon a yoke 130 which surroundsshaft 126. At one end, yoke 130 is pivoted to a fixed but adjustablepivot 131. The other end of yoke 130 is connected to piston rod 132projecting down from a double acting hydraulic cylinder 133 which ismounted on collar 134 of the machine frame F. The lifting motion of theworkhead and support structure is accomplished by introducing hydraulicfluid under pressure into cylinder 133 and raising the piston therein toraise rod 132, thereby swinging yoke 130 about pivot 131 to raise theblank B from the lower grinding position in FIG. 10 to the upperposition in which it engages locator 110. The means to feed the end millblank toward and retract it from the grinding wheel are as follows: Nearthe lower end of inner sleeve 121 is fastened collar which is shown inFIG. 18 as having two oppositely extending arms, 140a and 140)). Arm140a has connected to it one end of helical spring 142, the other end ofthe spring being attached to a suitable stationary point, as a portionof frame F. The pull of spring 142 on arm 140a biases collar 140 andinner sleeve 121 to move in a clockwise direction, viewed from above,which is the direction of retract movement which moves the workpieceaway from the grinding wheel.

The opposite arm 14Gb is moved counterclockwise to rotate the sleevewith the workhead in the counterclockwise direction, viewed from above.The means for so doing includes roller 143 which bears against arm 140band is mounted on one arm of bell crank 144. The other outwardlyextending arm of this bell crank is pivoted at 145 to a clevis on theupper end of rod 146. The pivot point is fixed, but preferablyadjustable.

Bell crank 144 is pivotally mounted on eccentric 150 on rock shaft 151.Rock shaft 151 is rotatably mounted in suitable bearings in brackets 152which are attached to suitable portions of the frame F. Rock shaft 151has nonrotatably attached to it arm 154, the outer end of the arm beingattached by linkage 155 to the upper end of vertically moving piston rod156. Piston rod 156 is attached to a piston moving within double-actinghydraulic cylinder 157, this cylinder being referred to as the in-feedcylinder, since introduction of hydraulic fluid under pressure into theupper end of the cylinder lowers the piston within the cylinder, therebydropping piston rod 156 and rotating rock shaft 151 in a clockwisedirection, viewed from the righthand end thereof in FIG. 18. Suchrotation of rock shaft 151 about its longitudinal axis rotates eccentric150 and pushes bell crank 144 against collar arm 140b. The movement ofthe bell crank is essentially one of rectilinear translation since pin145 moves only in a short are that is approximately horizontal. Thismotion of arm 14% is transmitted through inner sleeve 121 to the yoke120 supporting the head H, thereby moving head H and the workpiecetoward the grinding wheel.

When flow of hydraulic fluid is reversed through cylinder 157, reversemovement of yoke 120 in the grinding head to retract the workpiece fromthe grinding wheel is effected.

The third component of the compound movement of the workhead is aswinging movement of workhead H about trunnion axis 32. This swingingmovement of the workhead is initiated by supplying hydraulic fluid underpressure to double-acting cylinder 160, the fluid moving piston rod 161out of the cylinder. This motion of the piston rod is conveyed throughlink 162 to arm 163 which is fixed on inner shaft 126, as may be seen inFIGS. 9 and 18. The connection between arm 162 and shaft 126 preferablyincludes a spline or key 164 FIG. 9) in order to permit shaft 126 tomove vertically relative to arm 163, as already described.

To the top of shaft 126 FIG. is attached an arm 166. The outer end ofthis arm 166 is pin-connected to link 167, the other end of the linkbeing pin-connected to an arm 168 attached by screws 169 to trunnion 46to which workhead H is connected. Arms 166 and 168 are preferablyparallel to each other, and the linkage is such that the workhead isswung counterclockwise, as viewed from above (FIG. 15 through an arcequal to the angular movement of shaft 126.

Return swing of the workhead about axis 32 is accomplished by reversinghydraulic fluid flow through swing cylinder 160. Spring 171 is attachedat one end to arm 173 mounted on shaft 126 near arm 163, while spring172 is attached at one end to the outer end of arm 168. Both of thesereturn springs are attached at their other ends to suitable anchorages,as illustrated. The springs are to eliminate backlash.

Adjustable swing limiters 176 and 177 (FIG. 15) are utilized, moreparticularly for the primary, secondary relief grind, (to be describedhereinafter) to preselect and limit the angular swing of the workhead Hand end mill positioned therein, and thus determine the primary andsecondary relief angles for the grind of FIG. 5, but the limiter 177 isalso useful for the grind of FIG. 4. As here shown, such limiters, orstops, 176 and 177, are in the form of two plungers FIG. 15), which arealternatively, or selectively, engageable by the opposite ends of thelink 167. Each such plunger is movable longitudinally through, andscrewthreaded within, a corresponding bushing 178 mounted in walls 179of the hollow lower arm 46a of yoke 120, wherein are contained also thearms 166 and 168, and link 167. A knob 18] on the outer extremity ofeach such plunger can be calibrated in suitable angular divisions to beread against indicia on the bushing 178. In grinding the arcuate typegrind, sometimes referred to as form relief, the limiter plungers 176and 177 can be backed off, so as to have no limiting effect in makingthis grind. In such a case, the ends of the swing cylinder 160 set theend limits of swing. However, it is feasible and useful to use and setthe limiter 177 to terminate the swing of the workhead H at the end ofthe grinding stroke (FIG. 6C). Both of these limiters 176 and 177 areessential, however, to primary, secondary relief grinding asaccomplished by the improvements of the present invention, andconstitute component elements of the invention, as discussed below.

OPERATION CYCLE Assuming an arcuate form relief grind FIG. 4) to beused, limiter 177 is set to limit the swing of the workhead H to, forexample, 30 and logic circuit selector switch SL is thrown to theposition shown in full lines in FIG. 21A.

The flute selector is then set by means of knob to agree with the numberof flutes on the mill to be ground. The blank shown in FIG. 2 has fourflutes and so the two discs 87 and 88 are set, as shown in FIG. 7C toprovide four matching pairs of recesses or gates adapted to receivecontrol pin 96.

The machine is now placed in standby condition by pressing the button ofstart switch 174 (FIGS. 1 and 20). This energizes the electrical circuitshown in FIG. 20 and starts motor Ml which drives the pump P FIG. 21A)to provide hydraulic fluid under pressure for the control system.

As soon as hydraulic pressure reaches a safe value, pressure switch lPScloses and grindwheel spindle drive motor 36 (M2 in FIG. 20) starts. Atthis time, the workhead is in the raised position, holding the end millin the load position of FIG. 6A as a result of a swing back, an indexingrotation, and an elevation, which were the last operations of thepreceding workhead swing cycle (FIGS. 6E and 6F). The hydraulicconnections, fluid flow directions and position of valve SC for theirlast operations of the preceding cycle are shown in FIG. 21A, whereinhydraulic fluid flow is into the front end of swing cylinder 160 towithdraw plunger 161 and swing the workhead clockwise relative to theyoke (FIG. 6A). At the inner limit of this stroke, (whether byengagement of the plunger, with the cylinder bottom, or with a stop)rise of hydraulic pressure in the front end of cylinder to apredetermined level, conveyed to an air switch V2, switched an open 13line D leading to logic circuit terminal 13 into communication withpressure line 8. The pin 96 is at this time in a deep selector disk gap,valve spool 104 is in its uppermost position (FIG. 21A); and in thiscondition, the

increase in pressure in the line D leading from the now closed valve V2to the logic circuit via terminals 13 signaled the logic circuit FIG.21B) via line 12to actuate valve U to send hydraulic fluid into thelower end of cylinder 133, raising the workhead to theloadinglevel.

After loading, cycle startvalve 179 is actuated, and initiates theautomatic grinding cycle by supplying air from supply source S to thecontrol system shown in FIGS. 21A and 21Band causing it to takeovercontrol and perform automatically a programmed sequence ofoperations. First, the logic circuit (FIG. 21B) signals valve U viaterminals 12 to send hydraulic fluid to the upper end of cylinder 133,thereby dropping the workhead to the grind level in which blank Bisinthe full line position shown in FIG. 10, and also, after. a shortdelay introduced by a timer in the logic circuit, to apply hydraulicfluid to the chuck cylinder for chuck clamp piston 56 to clamp the endmill. Also, at this time, the logic circuit signals the control valve Fvia terminals to supply hydraulic fluid from pump P to feed cylinder 157to retract the plunger thereof. This FIGS. 15 and 18) rotates theworkhead support yoke 120 counterclockwise on axis 127 to feed the blankin toward the grindwheel as indicated in FIG. 21A and FIG. 6B. At thepredetermined limit of infeed, an air limit switch V3 is engaged andactuated to connect pressure line 8 to open logic circuit line 9. Thissignals the logic circuit to send a signal via line 11 to control valveSC to feed hydraulic fluid into the back end of swing cylinder 160,causing the plunger 161 thereof to extend to swing the workhead relativeto yoke 120 in a counterclockwise direction about axis 32, soswingingthe blank B along grinding wheel 31 as shown in FIG. 6C. At theend of this swing, determined by the setting of limit stop 177 and whichmay be about 30, hydraulic pressure rises behind the plunger, and in theconnection leading from the back end of cylinder 160 to switch V1 andoperates said switch V1 to connect open air line D to pressure line 8,sending pressure air into line D leading to the logic circuit viaterminals 14. This signals the logic circuit to act via line 15 tooperate valve F to cause re verse flow through feed cylinder 157, whichthereupon retracts the workhead and yoke 120, without swing back of theworkhead, as indicated in FIG. 6D. As the retraction is completed, limitswitch V4 is actuated and connects pressure lie 8 to line 10 to signalthe logic circuit to reverse the flow of hydraulic fluid through swingcylinder 160, and send it again into the front end of said cylinder.This it does with a pneumatic signal through line 11 to valve SC. Theworkhead and end mill blank B are thereby swung back (clockwise) aroundswing axis 32 as shown in FIG. 6B; and upon this return, switch V2 iscontrolled to supply a pressure signal to line D and terminals 13 of thelogic circuit, so as to initiate the indexing cycle.

This same sub-cycle is automatically repeated for each flute on a blankB. The control system is programmed by the flute selector toautomatically grind an end face 30a with reference to each flute inexactly the same manner and in sequence. After the last grind set by theflute selector, pin 96 drops into the gate in the periphery of theselector discs which is deeper than the other gates, thereby producingthe earlier described se-.

quence of operations which end thecycle, with the workhead elevated andcollet :nreleased, so that the tool holder canbe manually removedandthe: machine unloaded.

CONTROL SYSTEM The various movement of the workhead required to grindeach of the faces on the end of an end mill B could, of course, becarried out by hand. However, it is an objective of the presentinvention and one of its advantagesthat the sequence of the variousoperations be carried out automatically by a control system with greaterspeed, accuracy, and uniformity of product than is possible by manualoperation. To control the various operations, there has been providedthe airhydraulic system shown in detail in FIGS. 21A and 21B.

The major control functions are carried out in sequence by a network ofconventional pneumatic logic elements, shown particularly in FIG. 21B.These logic elements are known valves with the character shown in thelegend attached to FIG. 2113. In addition to the elements shown in thelegend, there are a number of position sensors which are basically limitvalves or switches actuated by the movement of parts of the workhead ofthe supporting structure therefor. These sensors are generallytwo-position valves, as shown diagrammatically in FIG. 21A inassociation with the component parts of the machine which actuate thesensors. The purpose of such sensors is to signal the completion ofcertain movements of the machine, thereby causing the control system tocomplete certain movements or to initiate other movements, as willbewell understood by those skilled in the art.

The construction of the logic circuit of FIGS. 21A and 21B is notdescribed in greater detail since it, per se, is not claimed and sinceother controlsystems may be used, also because the art of pneumaticlogic circuit control of sequencing of machine element movements is nowso well understood that such circuits can be readily constructed as aroutine matter by technitians skilled in the art to carry out any systemof sequential operations from requirements stated.

PRIMARY/SECONDARY RELIEF GRIND The present invention incorporates meanswhereby either the arcuate, form relief grind of FIG. 4, or the primary,secondary relief grind of FIG. 5, can be ac complished.

To set the logic circuit for the primary/secondary grind, selectorswitch SL is thrown to its alternate position in FIG. 21A, therebyaltering the control circuit of FIG. 218. With reference now to FIGS. 66to 6N, the end mill blank B, which in this case is tobe ground to theprimary/secondary relief form of FIG. 5, is returned at the end of eachgrind cycle to an angular position such as represented in FIG. 66. Theplane 47 again passes through the rotation axis of the grinding wheel31, and the pivot axis 32 again is substantially in this plane 47, andis parallel to the grindingwheel axis, or at least parallel to anelement of the grinding surface. The end mill blank, instead of havingbeen left at the end of the preceding cycle in a position with its axis58 parallel to plane 47, is instead at an adjusted primary relief angle4) of, for example, 15 relative to the plane 47. This angle, which mayrange as high as 20", is set

1. In a grinding machine for grinding end faces on an end mill, thecombination of: a frame; a grinding wheel rotatably mounted on saidframe; a workhead for holding the end mill with its longitudinal axis inpredetermined relation to said grinding wheel; a workhead carriagemovable on said frame to carry said workhead and end mill along apredetermined feed in path ending substantially normally to the grindingsurface of said grinding wheel, so as to engage an end portion of saidend mill with said grinding surface of said grinding wheel; means forimparting successive feed in movements to said workhead carriage to movesaid workhead along said path, a pivot mounting for said workhead onsaid carriage on an axis perpendicular to said path; adjustable stopmeans for limiting swing of said workhead about is pivot mounting onsaid carriage for establishing the longitudinal axis of said end mill attwo preselected angular spaced end limit positions relative to saidgrinding surface; means for swinging the workhead to position it and thEend mill held thereby in one and then the other of said end limitpositions in a timed sequence prior to successive feed in movements ofthe carriage along said predetermined path so that upon feed in movementat each position a predetermined different angular relief surface isformed on said end mill; and means for initiating feed in movements ofthe workhead carriage in response to arrival of the workhead at eachsaid preselected end limit positions.
 2. The subject matter of claim 1,including two manually and independently adjustable stops for settingsaid end limit positions of said workhead relative to said carriage. 3.The subject matter of claim 1, including a pivot mounting for saidcarriage on said frame, on an axis parallel to that of said workhead onsaid carriage, so arranged that said feed in path for said workhead isan arc approaching a grinding surface on said grinding wheelsubstantially normally thereto.
 4. The grinding machine according toclaim 3, wherein: the means for imparting feed in movements to theworkhead carriage and the means for swinging the workhead each comprisesa hydraulic cylinder and plunger assembly, and including meansresponsive to arrivals of the workhead at said end limit positions asmoved thereto by one of said cylinder and plunger assemblies foractivating the other of said cylinder and plunger assemblies to initiatefeed in movements of the workhead carriage.
 5. The grinding machineaccording to claim 2 in which one of said stops is adjustable toposition the workhead and the end mill held therein such that feed inmovement of said end mill against said grinding wheel at that positioncauses a primary relief surface to be ground on said ene mill at apredetermined angle with respect to the longitudinal axis of said endmill, and said other stop is adjustable to position said work head andthe end mill held therein such that feed in movement of said end mill inthat angular position causes a secondary relief surface to be formed onsaid end mill at predetermined angles with respect to said primaryrelief surface and the longitudinal axis of the end mill.
 6. Thegrinding machine according to claim 1 in which said workhead includes atleast one trunion mounted for relative rotational movement in saidcarriage, an arm member secured to said trunion for rotational movementwith said trunion and workhead relative to said carriage, and a pair ofstop members adjustably positionable in said carriage on opposite sidesof said arm member for limiting rotational movement of said arm,trunion, and workhead between predetermined positions.
 7. The grindingmachine according to claim 3 in which said pivot mounting for saidcarriage includes a depending sleeve mounted for relative rotationalmovement within same frame, means for selectively imparting rotationalmovement to said sleeve in response to the arrival of said workhead ateach of said preselected in limit positions, said workhead having atleast one trunion mounted in said carriage for relative rotationalmovement, said means for swinging said workhead to said limits includinga shaft extending coaxially through said depending sleeve, linkage meansconnecting one end of said shaft to said trunion whereby rotation ofsaid shaft relative to said sleeve causes rotary movement of saidtrunion and workhead relative to said carriage, means for impartingrotary movement to said shaft in response to the arrival of saidworkhead at each of said preselected limit positions, and said stopmeans including a pair of threaded members adjustably mounted withinsaid carriage for engagement by said linkage to limit rotationalmovement of said shaft and trunion between determined angular positions.